Naturally-conducted or intrinsic ventricular depolarizations have been recognized as being preferable over ventricular pacing in general and pacing in the right ventricular apex in particular. In order to minimize or greatly reduce ventricular pacing, pacing protocols have been developed that, in general, utilize an atrial based timing mode that promotes intrinsic conduction to the ventricles whenever possible. Illustrative protocols are described in U.S. Pat. No. 7,218,965 (Casavant), U.S. Pat. No. 6,772,005 (Casavant), and U.S. Pat. No. 7,248,924 (Casavant), all of which are incorporated herein by reference in their entireties.
Atrial based pacing performed in the context of minimizing ventricular pacing as discussed above reverts to dual chamber pacing in the event of AV conduction block. After switching to a dual chamber pacing mode, such as DDD, periodic AV conduction checks are scheduled. When AV conduction is again detected as signified by a ventricular sensed event following an atrial pacing pulse, atrial pacing is resumed to allow the more desirable naturally-conducted ventricular activation to occur.
An AV conduction check can sometimes result in a false positive detection of AV conduction in patients having AV conduction block and an idioventricular rhythm, premature ventricular contractions (PVCs), or other ventricular beats arising from the ventricular region of the heart and not conducted from the atrium. An idioventricular depolarization or a PVC may coincidentally occur during an AV conduction check, signifying, incorrectly, that AV conduction is intact.
In this situation, a false positive detection of AV conduction will cause conversion from dual chamber to atrial pacing and resets an AV conduction check timer. Since AV block is actually present, the pacemaker will quickly return to a dual chamber pacing mode, and a newly scheduled AV conduction check will again be performed. Frequent pacing mode switching and AV conduction checks are unnecessarily performed. Accordingly, a need remains for a device and method for delivering minimum ventricular pacing (MVP) that reduces the likelihood of frequent and unnecessary pacing mode switching and AV conduction checks.